1. Field of the Invention
The present invention relates to a composition for forming an insulation film that can form a coating film which excels in low dielectric constant, crack resistance and stress resistance, and an insulation film for a semiconductor device using this composition.
2. Description of the Drawing
A drop in the signal propagation speed by the parasitic capacity of an insulation film for a semiconductor device has been known, but the line delay did not have a major influence on an entire device at the generation in which the line space of a semiconductor device exceeds 1 μm. But the influence on the device speed becomes major when the line space is 1 μm or less, and in particular the influence of the parasitic capacity between the lines on the device speed will be significant if circuits are formed with a 0.1 μm or less line space in the future.
As the degree of integration of semiconductor integrated circuits increases and device density improves, the demand for multi-layer semiconductor devices is increasing, particularly. In this trend, the line space is becoming smaller, for example, due to the higher degree of integration, and the line delay caused by the increase in capacity between lines is becoming a problem. The line delay (T) is influenced by the line resistance (R) and the capacity between lines (C), and is given by the following Formula 7.T∝CR  (7)
In Formula 7, the relationship of ∈ (dielectric constant) and C is shown in Formula 8.C=∈o∈rS/d  (8)(where S is an electrode area, ∈o is the dielectric constant of a vacuum, ∈r is the dielectric constant of an insulation film, and d is a line space.) Therefore in order to decrease the line delay, decreasing the dielectric constant of an insulation film is effective. So in order to decrease the dielectric constant of an insulation film, an organic insulation film is used, or voids are introduced into the insulation film. For example, nano-clustering silica (NCS), made by Shokubai Kasei Industry (product name: Celamate NCS), is used. In such an insulation film material, clustering silica is formed using a quaternary alkyl amine as a catalyst. Also a low dielectric constant insulation film having an SiO bonding as the skeletal structure is formed by CVD or the like.
In this way, the skeletal structure of such low dielectric constant insulation films is, in many cases, SiO bonding. However, since copper as a material for wirings comes into an insulation film of which the skeletal structure is an SiO bonding, a barrier insulation film is required to be a cap of copper wires.
However the relative dielectric constant of a conventional cap insulation film by CVD is high, which interferes in further decreasing the dielectric constant of the insulation film. In the case of a coating type film by a spin counter, the relative dielectric constant can be decreased by using a polymer material for the insulation film, but the strength is not sufficient, which tends to cause a breakdown in the insulation film during a process where stress is applied, such as the chemical mechanical polishing (CMP) process, and the wire bonding process to connect electrodes to pads, and this insufficient stress resistance is a major cause in the drop in yield and reliability.
After serious research to solve these problems, it was found that a relative dielectric constant as low as 3.0 and a 10 GPa or more Young's modulus can be implemented if a method of forming a cap insulation film by the spin coat method and improving the strength by irradiating electron beams {see Japanese Unexamined Patent Application Publication No. 2003-297819 (Claims)}, a method of improving the strength by attaching a functional group which is condensed with the side chains to form cross-links {Japanese Published Patent Application No. 2005-513777 (Claims)}, etc. are provided.
However as a result of repeated testing to form a low dielectric constant silica type film on various semiconductor substrates using these methods and a conventionally known film forming method (spin coat method and other coating methods), it was discovered that a film having the above mentioned characteristics can be obtained, but cracks tend to occur probably due to the shrinking of film when about 50 nm of film, which is the actual film thickness used as a cap film, is being formed.
With the foregoing in view, it is an object of the present invention to provide a material for an insulation film which has a low dielectric constant, excellent stress resistance having sufficient strength, and excellent crack resistance by suppressing shrinkage during film formation. Other objects and advantages of the present invention will be clarified by the following description.